Fibrous stock blending control system

ABSTRACT

A system for controlling the composition of furnish in a papermaking mixing tank wherein a plurality of stocks are blended. A level transmitter generates a signal indicating the level of furnish in the mixing tank. This signal is compared in a comparator with a set point for the furnish level, any difference therebetween being indicative of a demand signal. The consistency and flow of each stock are measured at a stock valve connecting the respective stock supply with the mixing tank. A tons-per-hour calculator utilizes the consistency and stock flow measurements to derive a signal which is then ratioed with the demand signal. This ratio is then compared with a ratio set point, the difference therebetween controlling the stock valve. Additives may be controlled as above. Alternatively, density and flow of additive supply are utilized in an additive mass rate calculator to derive a mass rate signal which is ratioed with the total amount of fiber stock, this ratio then being compared with an additive ratio set point to provide an additive control signal.

United States Patent 721 Inventors Marion A. KeyesJV 3,490,689 1/1970 Him eiai.II..L.I.'.I.II1T.II "i'ih'ix South Beloit, 111.; John A. Gudaz, Beloit, Wis.; Yuan-Han Pmfwry Emml, m s' Leon Bfmhore Assistant Examiner-Alfred D Andrea, Jr. TsingAusunTex' AttorneyDu er Peterson Johnson& Westman 21 Appl. No. 785,307 gg [22] Filed Dec. 19, 1968 patfamed 1971 ABSTRACT: A system for controlling the composition of Asslgnee cof'pomfion furnish in a papermaking mixing tank wherein a plurality of Belmrwls' stocks are blended. A level transmitter generates a signal indicating the level of furnish in the mixing tank. This signal is compared in a comparator with a set point for the furnish [54] CRMOIES 3 8-55: I' i CONTROL SYSTEM level, any difference therebetween being indicative of a de g mand signal. The consistency and flow of each stock are mea- [52] US. Cl 162/253, sured at a stock valve connecting the respective stock supply 1 2, 1 7/4 7 1 2/1 8, 162/ 162/263 with the mixing tank. A tons-per-hour calculator utilizes the [51] Ill!- Cl D2lf 1/08, eonsisteney and stock flow measurements to derive a signal 605d 1 which is then ratioed with the demand signal. This ratio is then [50] Fkld of Search 162/252, compared with a ratio set point, the difference [herebetween 2 3 controlling the stock valve. Additives may be controlled as 467- above. Alternatively, density and flow of additive supply are utilized in an additive mass rate calculator to derive a mass Reierences C'ted rate signal which is ratioed with the total amount of fiber UNITED STATES PATENTS stock, this ratio then being compared with an additive ratio set 3,271,241 9/1966 Mumme 162/258 X point to provide an additive control signal.

CO/VSISTENC Y TRANS/ 4H 72' R FLOW TRANS/"I776? /\A 7/0 42 CONT/9011 [R sorrwaoo [0s STOCK SUPPL Y 14 123 34 34a 35 2 2 TONS l CONS/5 TENCY PER TRANSMITTER JCT/Ml DEM/1ND HOUR 38 c/ucu- FL 0W c TOR f TRANSMITTER 34b 42 RH RA T/O RAT/0 40c CONTROLLER 3U Pom/r 40 10 94 Z La/LATE 46b sT Z' fi w TONS/HOUR 4/] La v :Ii

ADD/T/l/E SUPPLY PATENTEOunv 16 I97! sum 2 [1F 3 17/ 2 321 34a 32a 32 7W5 L CONS/STENCY J yn 4 PER 4 TRANSMITTER Ohm/VD HOUR 341; 48 32c CALCU- FLOW 40a 1470/? 5 a TRANSMITTER R5 PAT/0 FL 0Wv /54 RAT/0 w/vrPoLLm CONTROLLER 5U POI/v7 40C 52 52c 40 4/ SOFTWOOD [23 5700/1 SUPPLY 4 50- 320 TONS L cm/s/smvcy 122 if W34 TRANSMITTER CALCU- HOW 88 LA TOR 52a 52b TRANSM/TTLR FLOW f54 CONTROLLER 52c HARDWOOD STOCK suPPLY 121M /364 m- Df/VS/TY TRANSMITTER FLOW rP/l/vsM/rrm FLOW F54 CONTROLLER ADD/T/VE 50/14 SUPPLY /4 12,4 i8 LEI/EL Aft fl TRANSMITTER r0 PAPER MACH/IVE FIBROUS STOCK BLENDING CONTROL SYSTEM BACKGROUND OF THE INVENTION 1 Field of the Invention This invention relates generally to paper making, and pertains more particularly to a control system for blending stocks and additives so that the resulting furnish will have a required composition.

2. Description of the Prior Art Blending systems have heretofore proportioned the various stock and additivecomponents on a volumetric basis. In other words, what has been measured in the past has been the amount of each fluid volume of stock or pulp entering the blend chest. Such systems have relied upon constant consistencies and have been insensitive to consistency variations. Consequently, the resulting furnish has not been of the required composition when such variations have occurred. Since different stock constituents or ingredients can vary rather widely as to price, the prior art systems have been disadvantageous as to quality and cost. Furthermore, stock pulp is usually prepared in batches and the consistency will vary from batch to batch for a given stock or additive, thereby resulting in what frequently turns out to be a paper of lesser grade than that desired.

SUMMARY OF THE INVENTION Accordingly, the present invention has for a general object the accurate control of the percentages of stocks and additives introduced into a blend chest or other mixing location in a manner such that the resulting furnish will have the required composition. More specifically, it is an aim of the present invention to provide a system that blends on the basis of mass flows of stocks and additives and not on the basis of volumetric flows as heretofore done, thereby obviating inaccuracies due to unequal consistencies and densities.

Another object of the invention is to provide a system of controlling the blending of stocks and additives that will be virtually immune to disturbances, such as deviations that have appeared in the past as far as batch variations are concerned. Also, our system obviates the need for an accurate selection of valve characteristics that control the stock and additive flows into the blend chest.

Still further, and additional object of the invention is to provide a structurally simplified system that requires relatively little hardware and allows an extremely easy method of operation.

Another object is to provide a system lending itself readily to employing digital techniques, doing so without requiring an objectionable amount of core storage.

Yet another object of the invention is to provide a stockblending control system that can without undue difi'iculty be incorporated into existing mixing systems.

Briefly, the present invention involves the selection of various set points representative of desired ratios of stock and additive components to the total of such components required for a given furnish, such ratios being on a bone dry basis. From the actual fluid volume of stock (pulp) or additive and the consistency thereof, the mass rate is calculated. The calculated mass rate is then ratioed with the demand for additional fluid stocks and additives required to maintain a particular level of furnish. The particular fluid flow is then corrected or adjusted with the consistency compensation reflected therein so that the actual ratio is equal to the desired ratio that has been selected, doing so for each component. Appropriate control loops are employed for making such an adjustment, the resulting furnish then possessing the requisite stock and additive composition.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1, 2 and 3 are block diagrams representing several different control loops that our invention may use.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first in detail to FIG. 1 a control system indicated generally by the reference numeral 10 has been depicted. Actually, the system 10 is comprised of several control sections 108, 101-! and 10A. The word section" has been deliberately chosen and as the description progresses it will be seen that the term is used in a sense that it is embracive of one (FIG. 1) or two (FIGS. 2 and 3) closed control loops.

Those familiar with the papermaking art will appreciate that various fibrous stocks are normally blended together in the making of a desired grade of paper. The most common ones include softwood (usually pine), hardwood and broke. However, it is believed that the invention can be adequately illustrated by utilizing only two such fiber stock components or materials. These have been rather arbitrarily selected as being softwood and hardwood. Hence, a batch-type softwood stock supply or pulp source has been indicated by the reference numeral 12S; similarly, a hardwood stock supply or pulp source has been indicated by the reference numeral 12H. For the sake of simplicity, a source of broke has not been presented. While various additives, such as clay, titanium dioxide or alum may be required, depending upon the type of paper to be manufactured, one typical additive may be considered to be alum. It really is not necessary to an understanding of the invention to select any particular additive; consequently, an additive supply source 12A may be considered to furnish whatever additive is required.

For each supply source 128, 12H and 12A there is a control valve 14. With respect to the softwood stock supply source 128 and the hardwood stock supply source 12H, it will be discerned that the two valves 14 pass their respective fluid stocksinto a conduit or pipe 16. Likewise, the valve 14 which is connected to the additive supply source 12A leads into a conduit or pipe 18. The conduits 16, 18 feed their respective pulp or fluid stocks and additive into a conventional blend chest 20 that has been diagrammatically diagrammatically and which in the illustrative situation constitutes the mixing situs or mixing point. As is customary, the blend chest 20 contains the furnish 22 which is agitated and then delivered through an outlet valve 24 to the paper making machine (not shown). It will be appreciated that the furnish 20 may pass through mixed stock refiners and other equipment before reaching the headbox from which the furnish or mixed stock is delivered onto a Fourdrinier wire.

To maintain reasonable operating conditions, the level of the furnish 22 in the blend chest 20 must be maintained within certain limits. Accordingly, a level transmitter 26 senses the pressure near the bottom of the chest 20 to provide a signal indicative of the tank level. This signal is forwarded to a summing junction or comparator 28 having input lines 280 and 28b. Actually, the level transmitter 26 is connected directly to the input line 28b, whereas a level set point signal is delivered to the comparator 28 via the input line 28a. Thus, the level transmitter 26 introduces into the comparator 28 a signal indicative of the level sensed in the chest 20, whereas the line 28a introduces a signal indicative of a desired level that should be maintained within the chest 20. Any diflerence between the two input signals is reflected as an error or difference signal which is forwarded by way of an output line 280 to a level controller 30. The level controller 30 has an output line 30a on which is carried a demand signal which is representative of the amount of furnish 22 needed to maintain the proper level in the chest 20.

Considering for the moment the control section 108, it will be seen that the line 30a leads to a divider 32, the function of which is to provide a ratio signal. More specifically, the divider 32 has a pair of input terminal 32a, 32b and an output terminal 320. The function of the input terminal 320 is to deliver to the divider 32 a signal representative of the amount of furnish 22 needed to maintain a desired level in the chest 20, this being the signal carried on the line 32a as explained above.

However, the input terminal 32b feeds into the divider a signal representative of the actual rate of dry softwood stock being delivered to the mixing point provided by the blend chest 20. In this regard, a tons per hour calculator 34 is included in the control section S, the calculator 34 having a pair of input lines 34a and 3412, as well as an output line 34c which is connected directly to the input terminal 32b of the divider 32. Connected 34a is a consistency transmitter 36 and connected to the input line 34b is a flow transmitter 38. It will be recognized that the two transmitters 36, 38 sense, respectively, the consistency (fiber to liquid ratio) and flow rate of the fluid stock passing through the valve 14 that is in circuit with the softwood stock supply source 128. At this stage, it will be helpful to explain that the calculator 34 multiplies the consistency and flow signals provided by the transmitters 36 and 38. In order to obtain the desired units, such as tons per hour, there is a multiplication by an appropriate constant which gives the desired conversion so that the output signal on the line 34a is truly representative of the particular units that have been selected (and which units are correlated with the units represented by the incoming signal on line 30a as determined by the level controller 30). While tons per hour have been selected, it will be understood that pounds per minute, kilograms per fortnight or any other mass flow per unit time designations could be used. It is important to appreciate, however, that the actual flow is measured and that the consistency of the flow is also measured, these measurements being used to compute the bone dry tons per hour (or whatever mass flow rate units are selected). It is only necessary to obtain a ratio of what is actually flowing in the way of a bone dry stock ingredient through the valve 14 with what is demanded. Hence, the signals applied to the input tenninals 32a and 32b are ratioed to provide a ratio signal on the output line 32c which is an actual bone dry ratio.

As far as the control section 108 is concerned, the set point representative of the amount of softwood in relation to the total number of components on a quantitative basis desired in the furnish 22 is represented by the designation RS. The set point signal RS is applied to a summing junction or comparator 40 by means of an input line 40a, whereas the ratio signal provided by the divider 32 is delivered to the comparator 40 through an input line 40b. Any difference or error between these two input signals appears as an error or difi'erence signal that is fed over an output line 400 to a ratio controller 42. It is, of course, the ratio controller 42 in this instance that adjusts the opening of the valve 14 so that the requisite amount of softwood fluid stock flows from the source 125 into the pipe or conduit 16 and then into the blend chest 20.

Recapitulating, what has been described provides a ratio loop that has a ratio set point signal RS that is compared to the calculated ratio signal that is a ratio of the actual fluid or pulp stock flow to the demand for furnish 22 in the blend chest 20. The valve 14 contained in the control section 108 is thereby positioned in accordance with the error or difference between the desired ratio set point signal RS and the computed or actual ratio signal as determined by the comparator 40.

Since it has already been pointed out that any number of fiber stocks can be ratioed but that two have been typically selected for illustrating the invention, it will be appreciated that the control section 10H includes hardware identical to that contained in the control section 105. However, since the ratio of hardwood stock material to the total material or components required in the furnish 22 will differ from what is required as far as softwood is concerned, the set point signal has been designated by the letters RH. In this way, the control valve 14 associated with the control section 10H is adjusted in the same manner as is the control valve 14 associated with the control section 108 but in accordance with data pertaining to the rate of flow of the pulp containing hardwood stock material rather than softwood stock material.

While it is possible to ratio additives in the same fashion as fiber stocks are ratioed, the usual practice is to take the entire amount of fiber stock components that are being added to the blend chest 20 and ratio the additives to the total amount of fiber stock material. Therefore, FIG. 1 as set forth allows two different approaches to be followed with respect to the introduction of additives. To render FIG. 1 as simple as possible, a switch 44 has been schematically portrayed having three terminals 44a, 44b and 44c. When the switch 44 is in its solid line position as pictured, that is, bridging the terminal 44a and 44b, the divider 32 for the additive control section 10A has its input line 32a connected directly to the output line 30a extending from the level controller 30. When so connected, the additive control section 10A functions in an identical manner to the control sections 105 and 10H. Of course, the value for the set point signal RA is selected for the amount of additive that is to be introduced in proportion to the total components that are to constitute the furnish 22. Since the additive fluid is normally sensed on a density basis rather than consistency, although the two are certainly interrelated, the transmitter for sensing the density has been labeled 36A. Also, since the calculator is intended to accept a density signal from the transmitter 36A, the calculator in the control section 10A has been designated by the reference numeral 34A. The computation, though, is the same as in the control sections 108 and 10H. Consequently, in this particular arrangement, that is when the switch 44 is in its solid line position, the valve 14 for the control section 10A is adjusted so as to pass additive in fluid form received from the supply source 12A at a fluid flow rate determined by the difference or error signal delivered to its ratio controller 42 from the comparator 40.

It is when the switch 44 is shifted to its dotted position so that it bridges the terminals 44b and 440 that the operation is slightly different. In this situation, there is a summing circuit 46 that is made use of. The circuit 46 has a first input terminal 46a and a second input terminal 46b, the first terminal being connected to the output line 34c of the calculator 34 belonging to the control section 105 whereas the second terminal 46b is similarly connected to the output line 34cof the calculator 34 for the control section 10H. The summing circuit 46 has an output terminal 460 that is connected to the switch terminal 44b so that instead of having the input terminal 32a for the divider 32 of the control section 10A connected to the line 30a, it is connected to the output terminal 46c so that the ratio signal delivered to the input line belonging to the comparator 40 for the control section 10A is on the basis of the total calculated tons per hour for all (only two depicted) pulp or fluid stock flow rates rather than on the demanded tons per hour as determined by the level controller 30. The operation, however, is the same as far as the control loops are concerned. Hence, in the last situation, the ratio set points are really summed to percent and the level control is essentially done with the fiber stocks, namely the softwood and hardwood, and not with the additive that would be introduced with the control section 10A. Hence, the additive will be added on the basis, say, of pounds of dry additive per ton of total dry stock. Once again, though, the particular units are not important.

Passing now to a brief description of FIG. 2, it should be pointed out at the outset that instead of performing the ratio operation with one control loop as in each section 108, 10H, 10A of FIG. 1, the ratio operation is taken care of in one loop and the flow control in a different loop. In other words, the functions which were combined into a single loop as set forth in FIG. I are now accomplished in two loops. Owing to this basic difference, the control system set forth in FIG. 2 has been given the reference numeral 50 and the several control sections constituting said system 50 have been denoted by the reference numerals 50S, 50H and 50A.

The same signal representative of the need or demand for furnish 22 in the blend chest 20 is delivered via the line 30a to the various dividers 32. Since various parts of the system 50 involve the use of identical parts, it should be explained that identical parts have been given the same reference numerals. Hence, the ratio signal delivered via the output terminal 320 of each divider 32 is compared with the particular set point RS,

RH and RA. With respect to the control section 508, the difference or error is fed via the output line 400 to the ratio controller 42. It is the output signal from the ratio controller 42 in this instance that is used as a flow set point and is applied to the input line 34b of the calculator 34. Hence, instead of having the input line 34b connected directly to the flow transmitter 38, it is connected directly to the ratio controller 42. However, the consistency transmitter 36 remains connected to the other input line 34a belonging to the calculator 34 as in the system illustrated in FIG. 1.

A flow control loop, as contrasted with the above-referred to ratio loop, includes a summing junction or comparator 52 having a first input line 520 that is connected to the ratio controller 42 as is the input line 34b leading to the calculator 34. The comparator 52 has a second input line 52b that receives the fluid rate of flow signal from the transmitter 38. A comparison is made between the two signals impressed on the input lines 52a and 52b so as to provide an output signal on the line 52c that is indicative of any difference between the two input signals. It is the output line 520 that extends to a flow controller 54 that actually positions the valve 14 in each of the control sections 508, 50H and 50A.

For the sake of simplicity, the system 50 may be considered as consisting of the three control sections 508, 50H and 50A, all receiving level information in the same manner. Hence, the summing provided by the circuit 46 in FIG. 1 has not been applied to the system 50 of FIG. 2.

Having presented the systems labeled l0 and 50, the system 60 shown in FIG. 3 should be easily understood. In this instance, the system 60 is composed of control sections 60S, 60H and 60A. It will be observed that in this situation, the calculator 34 for each of the control sections 60S, 60H and 60A has its input lines 34a and 34b connected as they are connected in the system 10 of FIG. 1. However, the output line 340 is connected to the input line 52b of the comparator 52. In this way, the calculated tons per hour signal, or in the case of the additive the additive mass rate signal, is delivered into the comparator 52 and compared with the signal coming in over the input line 52a.

In addition to feeding a signal to the comparator 52 over the input line 520, the ratio controller 42 delivers its output signal to the input terminal 54b of the divider 34. Consequently, the ratio signal that is derived from each divider 34, as far as the control sections 605 and 60H are concerned, is then used as the ratio signal that is compared with the particular set point signal RS and RH, as the case may be.

Corresponding to the summing circuit 46 of FIG. 1 is a summing circuit 62 for the additive control section 60A, the circuit 62 having three input terminals 62a, 62b and 620 plus an output terminal 62d. The several input terminals 62a, 62b and 620 are connected to the calculators 34 of the three control sections 608, 60H and 60A. The summed signal delivered via the output terminal 62d is forwarded to a summing junction or a comparator 64 having a pair of input lines 64a, 64b and an output line 640. in this way, the set point signal representative of the desired ratio of additive to the total components in the furnish 22 is compared with the summed signal from the summing circuit 62 and any difference or error is impressed on the input of a ratio controller 66 which in turn positions the valve 14 for the particular control section 60A. The additive loop in this instance sums the total stock flows plus the additive flow and the additive is blended on the sum of these various flows. The operation, however, is the same as far as all of the other stock and additive loops are concerned.

We claim:

1. A system for controlling the composition of furnish in a mixing means for delivery to a paper machine comprising valve means for adjusting the rate of flow of one fluid stock to said mixing means said fluid stock containing a given stock component therein, means for sensing the actual rate of flow of said fluid stock through said valve means, means for sensing the consistency of said fluid stock as influenced by the amount of said component contained therein, means for sensing the demand for fluid stock needed to maintain the amount of furnish at a desired value in said mixing means, and means responsive to said flow rate sensing means, said consistency sensing means and said demand sensing means for adjusting said valve means in a direction to maintain a desired ratio of said given stock component to the total of stock components required in said furnish, said responsive means including a calculator connected to said consistency sensing means and to said flow sensing means for generating an output derived from said consistency and fluid stock flow.

2. A system for controlling the composition of furnish as set forth in claim 1 in which said responsive means also includes means connected to said calculator and to said demand sensing means for providing a signal representative of the actual ratio of the output from said calculator to the output from said demand sensing means.

3. A system for controlling the composition of furnish as set forth in claim 2 in which said responsive means further includes a comparator for comparing said actual ratio signal to a set point signal representative of said desired ratio, any difference between said actual and desired ratio signals being utilized in the adjusting of said valve means.

4. A system for controlling the composition of furnish in a mixing means for delivery to a paper machine comprising means providing a set point signal representative of a desired ratio of one bone dry stock component to the total of such components required in said furnish, means providing a signal which is a measure of the total demand for fluid stock required in said mixing means, means providing a computed signal which is a measure of the actual rate of flow and also the consistency of fluid stock to said mixing means, said computed signal providing means including a calculator for computing said computed signal from said actual rate of flow and consistency, said fluid stock having said one component contained therein, and means for adjusting the actual rate of flow of said fluid stock to said mixing means in response to said demand and computed signals, whereby the adjustment of the rate of flow of fluid stock controls the amount of said one bone dry stock component in relation to the total of said com ponents required in said furnish.

5. A system for controlling the composition of furnish as set forth in claim 4 in which said adjusting means includes means for providing a derived signal which is a measure of the ratio of said computed signal and said demand signal, and said adjusting means further including a comparator for comparing said derived ratio signal with said desired ratio signal, any difference therebetween causing said adjustment of the rate of flow of said fluid stock.

6. A system for controlling the composition of furnish in a mixing means for delivery to a paper machine comprising means providing a set point signal representative of a desired ratio of one bone dry stock component to the total of such components, means providing a signal which is a measure of the demand for fluid stocks required at said mixing point, means providing an actual signal which is a measure of the rate of flow and consistency of fluid stock in said mixing means, said fluid stock having said one component contained therein, means deriving a signal representative of the ratio of said actual and demand signals, means comparing said derived ratio signal with said set point ratio signal to produce an error signal which is a measure of any difference therebetween, and means for adjusting the rate of flow of said fluid stock containing therein said one component in accordance with said error signal.

7. A system for controlling the composition of furnish as set forth in claim 6 in which said adjusting means includes a valve, the position of which valve influences said rate of flow, and in which said actual signal means includes a flow transmitter for determining the rate of fluid stock flow through said valve, a consistency transmitter for determining the consistency of said stock flow and a calculator, said calculator computing said actual signal from said rate and consistency of the fluid stock flow.

8. A system for controlling the composition of furnish as set forth in claim 7 in which said means providing a demand signal includes a level transmitter for providing a signal representative of the level of furnish at said mixing point, a comparator for comparing said level signal with a set point signal indicative of a desired level of furnish, any difference between said level and level set point signals providing said demand signal.

9. A system for controlling the composition of furnish in a mixing means for delivery to a paper machine comprising a valve for adjusting the rate of flow of fluid stock to said mixing means, said fluid stock containing a required stock component therein, a flow transmitter for providing a signal which is the measure of the rate of fluid stock flow through said valve, a consistency transmitter for providing a signal which is a measure of the consistency of said fluid stock as determined by the amount of said component contained therein, calculator means providing a computed signal indicative of the mass rate of flow of said component as derived from said fluid flow rate and consistency signals, a level transmitter for providing a signal which is a measure of the level of furnish in said mixing means, comparator means for comparing said level signal with a set point signal which is indicative of a desired level of furnish to be maintained at said mixing point, a level controller responsive to any difference between said level set point signal and the level signal provided by said level transmitter for providing a demand signal that is a measure of the amount of furnish needed to maintain a desired level of furnish in said mixing means, means for ratioing said mass rate of flow signal from said calculator means with said demand signal from said level controller to provide an actual ratio signal, means comparing said actual ratio signal with a set point signal representative of a desired ratio of said required stock component to the total of the components required in said furnish, and means responsive to any diflerence between said actual and desired ratio signals for positioning said valve to adjust the rate of flow of fluid stock to said mixing means in accordance with the value of any such difference.

10. A system for controlling the composition of furnish as set forth in claim 9 including an additional valve for adjusting the rate of flow of a second fluid stock to said mixing means, said second fluid stock containing a second required stock component therein, a second flow transmitter for providing a signal which is the measure of the rate of flow of said second fluid stock through said second valve, a second consistency transmitter for providing a signal which is a measure of the consistency of said second fluid stock as determined by the amount of said second component contained therein, second calculator means providing a signal indicative of the mass rate of flow of said second component computed from said second flow rate and consistency signals, means providing a signal derived from the ratio of said second mass rate of flow signal and said demand signal provided by said level controller, and means for comparing said second derived ratio signal with a set point signal representative of a desired ratio of said second component to the total of components required in said mixing means, and means for positioning said second valve in accordance with any difference between said second derived and set point ratio signals.

11. A system for controlling the composition of furnish as set forth in claim 10 including a third valve for adjusting the rate of flow of a third fluid to said mixing means, said third fluid containing an additive component therein, a third flow transmitter for providing a signal which is the measure of the rate of flow of said additive-containing fluid through said third valve, a density transmitter for providing a signal which is a measure of the density of said additive-containing fluid as determined by the amount of additive component therein, third calculator means providing a signal indicative of the mass rate of flow of said additive component computed from said additive flow rate and density signals, means providing an additive reference signal, means for ratioing said computed additive mass rate of flow signal with said reference signal to provide a third derived ratio signal, and means for comparing said third derived ratio signal with a set point signal representative of a desired ratio of additive component to the total of stock components required in said mixing means, and means for positioning said third valve in accordance with any difference between said third derived and set point ratio signals.

12. A system for controlling the composition of furnish as set forth in claim 11 in which said means for providing said additive reference signal connects said level controller to said additive ratioing means, whereby said demand signal constitutes the additive reference signal.

13. A system for controlling the composition of furnish as set forth in claim 11 in which said means for providing a reference signal includes a summing circuit having a pair of input terminals connected to said first and second calculator means and having an output terminal connected to said additive ratioing means, whereby the sum of said computed mass rate of flow signals constitutes said reference signal.

14. A system for controlling the composition of furnish in a mixing means for delivery to a paper machine comprising a first valve for adjusting the rate of flow of one fluid stock to said mixing means, said fluid stock containing a required stock component therein, a second valve for adjusting the rate of flow of a second fluid stock to said mixing point, said second fluid stock containing a different required stock component therein, a third valve for adjusting the rate of additive fluid to said mixing point, said additive fluid containing a required additive component therein, a flow transmitter for each valve for providing respective signals each of which is a measure of the rate of fluid stock or additive flow through its particular valve, a consistency transmitter for each valve for providing signals which are measures of the consistency of each fluid flow therethrough as determined by the amount of stock or additive component therein, a calculator for each valve providing signals indicative of the various mass rates of flow of said components and additive as computed from said fluid flow rates and consistency signals, means for summing the signals computed by the calculators associated with said first and second valves to provide a summed signal indicative of the summed mass rate of flow of said stock components, means providing a demand signal which is a measure of the amount of fluid stock needed to maintain the furnish in said mixing means at a desired level, a first means for providing a derived ratio signal representative of the ratio between the first mass rate of flow signal and said demand signal, comparator means for comparing said derived ratio signal with a set point signal representative of a desired ratio of said first stock component to the total of said stock components required in said furnish, and means responsive to any difference between said derived and desired ratio signals for controlling said first valve in accordance with the value of said difference to thereby adjust the rate of flow of said first fluid stock and hence the amount of stock component delivered to said mixing means, second means for providing a derived ratio signal indicative of the ratio between said second mass rate of flow signal and said demand signal, means comparing said second derived ratio signal with a desired set point signal representative of the desired ratio of said second stock component to the total of said components required in the furnish, and means for positioning said second valve in accordance with any difference between said second derived ratio signals, and means for providing a derived ratio signal representative of the ratio between said mass rate of flow signal from said additive mass rate calculator and said summed signal, and means for comparing said derived additive ratio signal with a set point signal representative of the desired amount of additive with respect to the total stock components required in said mixing means, and means for positioning said third valve in accordance with any difference between said derived and desired additive ratio signals.

'15. A system for controlling the composition of furnish in a mixing means for delivery to a paper machine comprising a valve for adjusting the rate of flow of fluid stock to said mixing means, said fluid stock containing a required stock component therein, a flow transmitter for providing a signal which is a measure of the rate of fluid stock flow through said valve, a consistency transmitter for providing a signal which is a measure of the consistency of said fluid stock as determined by the amount of said components contained therein, a calculator having a pair of input lines and an output line, said input lines being connected to said transmitters so that said output line carries thereon a signal indicative of the mass rate of flow of said component computed from said flow and consistency signals, means providing a demand signal which is a measure of the amount of fluid stock needed to maintain the furnish in said mixing means at a desired level, means providing a derived signal which is indicative of the ratio between a difference signal and said demand signal, a comparator for comparing the derived ratio signal with a set point representative of a desired ratio of said stock component to the total components required in said furnish, any difference therebetween constituting said difference signal, a second comparator for comparing the output signal from said calculator with said difference signal, and flow controller responsive to any difference between said output signal from said calculator and said difference signal for positioning said valve in accordance with the value of said difference to thereby vary the rate of flow of fluid stock so as to more precisely introduce into said furnish in said mixing means an amount of stock component in relation to the total components required in said furnish as called for by said set point t I i i l UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3.620.915 Date November 16. 1971 Marion A. Keyes, IV, John A. Gudaz & Yuan-Hao Tsing It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Iolumn 1, line 4-6, "and" Should be an-. Column 2,' line 38, 1

lelete "diagrammatically" (second occurrence) and insert therefore -presented-; line 70, "terminal" shoulfi be terminals-. Iolumn 3, line 8, after "Connected" insert -to the input line. Io'lumn 4, line 7', "terminal" should be -terminals. Column 5, .ine 71, after "means" in sert Column 8, line 62, after' ierived", first occurrence, insert and desired Signed and sealed this 27th day of June 1972.

(SEAL) Attest: r

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner oi Patents 

2. A system for controlling the composition of furnish as set forth in claim 1 in which said responsive means also includes means connected to said calculator and to said demand sensing means for providing a signal representative of the actual ratio of the output from said calculator to the output from said demand sensing means.
 3. A system for controlling the composition of furnish as set forth in claim 2 in which said responsive means further includes a comparator for comparing said actual ratio signal to a set point signal representative of said desired ratio, any difference between said actual and desired ratio signals being utilized in the adjusting of said valve means.
 4. A system for controlling the composition of furnish in a mixing means for delivery to a paper machine comprising means providing a set point signal representative of a desired ratio of one bone dry stock component to the total of such components required in said furnish, means providing a signal which is a measure of the total demand for fluid stock required in said mixing means, means providing a computed signal which is a measure of the actual rate of flow and also the consistency of fluid stock to said mixing means, said computed signal providing means including a calculator for computing said computed signal from said actual rate of flow and consistency, said fluid stock having said one component contained therein, and means for adjusting the actual rate of flow of said fluid stock to said mixing means in response to said demand and computed signals, whereby the adjustment of the rate of flow of fluid stock controls the amount of said one bone dry stock component in relation to the total of said components required in said furnish.
 5. A system for controlling the composition of furnish as set forth in claim 4 in which said adjusting means includes means for providing a derived signal which is a measure of the ratio of said computed signal and said demand signal, and said adjusting means further including a comparator for comparing said derived ratio signal with said desired ratio signal, any difference therebetween causing said adjustment of the rate of flow of said fluid stock.
 6. A system for controlling the composition of furnish in a mixing means for delivery to a paper machine comprising means providing a set point signal representative of a desired ratio of one bone dry stock component to the total of such components, means providing a signal which is a measure of the demand for fluid stocks required at said mixing point, means providing an actual signal which is a measure of the rate of flow and consistency of fluid stock in said mixing means, said fluid stock having said one component contained therein, means deriving a signal representative of the ratio of said actual and demand signals, means comparing said derived ratio signal with said set point ratio signal to produce an error signal which is a measure of any difference therebetween, and means for adjusting the rate of flow of said fluid stock containing therein said one component in accordance with said error signal.
 7. A system for controlling the composition of furnish as set forth in claim 6 in which said adjusting means includes a valve, the position of which valve influences said rate of flow, and in which said actual signal means includes a flow transmitter for determining the rate of fluid stock flow through said valve, a consistency transmitter for determining the consistency of said stock flow and a calculator, said calculator computing said actual signal from said rate and consistency of the fluid stock flow.
 8. A system for controlling the composition of furnish as set forth in claim 7 in which said means providing a demand signal includes a level transmitter for providing a signal representative of the level of furnish at said mixing point, a comparator for comparing said level signal with a set point signal indicative of a desired level of furnish, any difference betwEen said level and level set point signals providing said demand signal.
 9. A system for controlling the composition of furnish in a mixing means for delivery to a paper machine comprising a valve for adjusting the rate of flow of fluid stock to said mixing means, said fluid stock containing a required stock component therein, a flow transmitter for providing a signal which is the measure of the rate of fluid stock flow through said valve, a consistency transmitter for providing a signal which is a measure of the consistency of said fluid stock as determined by the amount of said component contained therein, calculator means providing a computed signal indicative of the mass rate of flow of said component as derived from said fluid flow rate and consistency signals, a level transmitter for providing a signal which is a measure of the level of furnish in said mixing means, comparator means for comparing said level signal with a set point signal which is indicative of a desired level of furnish to be maintained at said mixing point, a level controller responsive to any difference between said level set point signal and the level signal provided by said level transmitter for providing a demand signal that is a measure of the amount of furnish needed to maintain a desired level of furnish in said mixing means, means for ratioing said mass rate of flow signal from said calculator means with said demand signal from said level controller to provide an actual ratio signal, means comparing said actual ratio signal with a set point signal representative of a desired ratio of said required stock component to the total of the components required in said furnish, and means responsive to any difference between said actual and desired ratio signals for positioning said valve to adjust the rate of flow of fluid stock to said mixing means in accordance with the value of any such difference.
 10. A system for controlling the composition of furnish as set forth in claim 9 including an additional valve for adjusting the rate of flow of a second fluid stock to said mixing means, said second fluid stock containing a second required stock component therein, a second flow transmitter for providing a signal which is the measure of the rate of flow of said second fluid stock through said second valve, a second consistency transmitter for providing a signal which is a measure of the consistency of said second fluid stock as determined by the amount of said second component contained therein, second calculator means providing a signal indicative of the mass rate of flow of said second component computed from said second flow rate and consistency signals, means providing a signal derived from the ratio of said second mass rate of flow signal and said demand signal provided by said level controller, and means for comparing said second derived ratio signal with a set point signal representative of a desired ratio of said second component to the total of components required in said mixing means, and means for positioning said second valve in accordance with any difference between said second derived and set point ratio signals.
 11. A system for controlling the composition of furnish as set forth in claim 10 including a third valve for adjusting the rate of flow of a third fluid to said mixing means, said third fluid containing an additive component therein, a third flow transmitter for providing a signal which is the measure of the rate of flow of said additive-containing fluid through said third valve, a density transmitter for providing a signal which is a measure of the density of said additive-containing fluid as determined by the amount of additive component therein, third calculator means providing a signal indicative of the mass rate of flow of said additive component computed from said additive flow rate and density signals, means providing an additive reference signal, means for ratioing said computed additive mass rate of flow signal with said reference signal to provide a third derived ratio siGnal, and means for comparing said third derived ratio signal with a set point signal representative of a desired ratio of additive component to the total of stock components required in said mixing means, and means for positioning said third valve in accordance with any difference between said third derived and set point ratio signals.
 12. A system for controlling the composition of furnish as set forth in claim 11 in which said means for providing said additive reference signal connects said level controller to said additive ratioing means, whereby said demand signal constitutes the additive reference signal.
 13. A system for controlling the composition of furnish as set forth in claim 11 in which said means for providing a reference signal includes a summing circuit having a pair of input terminals connected to said first and second calculator means and having an output terminal connected to said additive ratioing means, whereby the sum of said computed mass rate of flow signals constitutes said reference signal.
 14. A system for controlling the composition of furnish in a mixing means for delivery to a paper machine comprising a first valve for adjusting the rate of flow of one fluid stock to said mixing means, said fluid stock containing a required stock component therein, a second valve for adjusting the rate of flow of a second fluid stock to said mixing point, said second fluid stock containing a different required stock component therein, a third valve for adjusting the rate of additive fluid to said mixing point, said additive fluid containing a required additive component therein, a flow transmitter for each valve for providing respective signals each of which is a measure of the rate of fluid stock or additive flow through its particular valve, a consistency transmitter for each valve for providing signals which are measures of the consistency of each fluid flow therethrough as determined by the amount of stock or additive component therein, a calculator for each valve providing signals indicative of the various mass rates of flow of said components and additive as computed from said fluid flow rates and consistency signals, means for summing the signals computed by the calculators associated with said first and second valves to provide a summed signal indicative of the summed mass rate of flow of said stock components, means providing a demand signal which is a measure of the amount of fluid stock needed to maintain the furnish in said mixing means at a desired level, a first means for providing a derived ratio signal representative of the ratio between the first mass rate of flow signal and said demand signal, comparator means for comparing said derived ratio signal with a set point signal representative of a desired ratio of said first stock component to the total of said stock components required in said furnish, and means responsive to any difference between said derived and desired ratio signals for controlling said first valve in accordance with the value of said difference to thereby adjust the rate of flow of said first fluid stock and hence the amount of stock component delivered to said mixing means, second means for providing a derived ratio signal indicative of the ratio between said second mass rate of flow signal and said demand signal, means comparing said second derived ratio signal with a desired set point signal representative of the desired ratio of said second stock component to the total of said components required in the furnish, and means for positioning said second valve in accordance with any difference between said second derived ratio signals, and means for providing a derived ratio signal representative of the ratio between said mass rate of flow signal from said additive mass rate calculator and said summed signal, and means for comparing said derived additive ratio signal with a set point signal representative of the desired amount of additive with respect to the total stock components required in said mixing means, and meaNs for positioning said third valve in accordance with any difference between said derived and desired additive ratio signals.
 15. A system for controlling the composition of furnish in a mixing means for delivery to a paper machine comprising a valve for adjusting the rate of flow of fluid stock to said mixing means, said fluid stock containing a required stock component therein, a flow transmitter for providing a signal which is a measure of the rate of fluid stock flow through said valve, a consistency transmitter for providing a signal which is a measure of the consistency of said fluid stock as determined by the amount of said components contained therein, a calculator having a pair of input lines and an output line, said input lines being connected to said transmitters so that said output line carries thereon a signal indicative of the mass rate of flow of said component computed from said flow and consistency signals, means providing a demand signal which is a measure of the amount of fluid stock needed to maintain the furnish in said mixing means at a desired level, means providing a derived signal which is indicative of the ratio between a difference signal and said demand signal, a comparator for comparing the derived ratio signal with a set point representative of a desired ratio of said stock component to the total components required in said furnish, any difference therebetween constituting said difference signal, a second comparator for comparing the output signal from said calculator with said difference signal, and flow controller responsive to any difference between said output signal from said calculator and said difference signal for positioning said valve in accordance with the value of said difference to thereby vary the rate of flow of fluid stock so as to more precisely introduce into said furnish in said mixing means an amount of stock component in relation to the total components required in said furnish as called for by said set point. 